1. Field of the Invention
The present invention relates to a receiving apparatus and method, which perform reception using a clock signal having no correlation with the data rate or phase of a signal to be received.
2. Description of the Related Art
As an example of the conventional asynchronous signal receiving technique, start/stop synchronization in RS232C will be described. An RS232C communication use a signal sequence including one start bit, a data bit sequence of 6 to 8 bits that follows the start bit, a parity bit, and a stop bit. In order to receive this signal sequence, a receiving circuit comprises a start bit detection unit, phase conversion unit, and data fetch unit. As an oscillator for reception, the receiving circuit comprises a sampling clock that operates at several MHz, a communication clock that approximately matches the data rate determined in the specification, and a sync clock which is synchronized with a signal outside a receiving apparatus (for example, see JP-A 2003-348059 [KOKAI]).
A general signal receiving sequence in RS232C is as follows. If a signal of 1200 bps is input as receiving data, the start bit detection unit detects an input of a start bit by a sampling clock. The phase conversion unit is controlled based on this detection result to convert the phase of a 1200-Hz communication clock to an optimal value. In this phase state, a data bit sequence, parity bit, and stop bit that follow the start bit are received. The received data sequence is temporarily stored in a buffer, and is handled as a data signal by a sync clock.
In the related art, as described above, the receiving apparatus requires a plurality of high-precision clock signals, resulting in increases in circuit scale, consumption power, and cost. Even when a plurality of clocks are combined into one, this clock is required to have high precision, and expensive external components with a large size such as a temperature-compensated quartz oscillator and the like are required.
In this way, the conventional asynchronous signal receiving technique requires a high-precision apparatus as clocks of a receiving system to attain start/stop synchronization, thus posing problems of increases in cost, apparatus scale, and consumption power.